The syntheses of a series of metal chelating macrocycles, including the natural product enterobactin, are proposed. The project will test the utility of transition metal templates to effect hyperentropic closures of macrocycles in the enterobactin class. Synthetic materials will be screened for antimicrobial activity, and for their ability to induce iron excretion in iron-overloaded test animals. The synthetic chelating agents may be of value as antibiotics or in treatment of patients undergoing continual transfusion therapy (e.g., patients afflicted with Cooley's anemia (beta-thalassemia major or primary erythroblastic anemia)). Radiolabelled analogues of enterobactin will be produced in order to test their capacity to bind to the ferric-enterobactin receptor.